In the idiopathic inflammatory myopathies, disease pathogenesis remains largely undefined. However, we have recently published work demonstrating that immunization of different NOD and C57BL/6 congenic strains with murine histidyl-tRNA synthetase (Jo-1) generates muscle and lung inflammation resembling features of the anti-synthetase syndrome. The experimental approach outlined in this application extends these earlier studies through functional manipulation of dendritic cell (DC) phenotype to define characteristics of the Jo-1-specific immune response contributing to disease expression. Specific Aim 1 employs different in vitro cytokine preparations and maturation stimuli to generate Jo-1-loaded DCs capable of skewing toward Th1, Th2, or Th17 immune responses targeting this antigen. Subsequent immunization of NOD and C57BL/6 congenic mice with Jo- 1-pulsed DCs cultivated under defined conditions will highlight the impact of antigen-specific T cell polarization on tissue inflammation in comparison to Jo-1/CFA immunization. Adoptive transfer of organ-infiltrating lymphocytes from DC-immunized to naive mice will firmly establish the relationship between Jo-1-specific autoimmune responses and the anti-synthetase syndrome. Parallel measurement of CFSE-labeled T cell proliferative responses and intracellular cytokine staining of antigen-challenged lymphocytes derived from spleen and organ-draining lymph nodes of DC-immunized mice will further link the observed tissue phenotype to Th17 and/or Th1-polarized, Jo-1-specific T cell responses. In contrast, use of alternative cytokine conditioning in Specific Aim 2 will generate Jo-1-loaded "tolerogenic" DCs capable of blocking disease induction and, more importantly, re-establishing tolerance in existing disease. Complementing the in vivo assessment of Jo-1-pulsed tolerogenic DC immunization in disease preventioNot applicable.melioration, in vitro transwell mixing and antibody blocking experiments will define the relative contribution of anergy, bystander suppression, and contact-mediated inhibition to antigen-specific regulatory T cell function. The mechanistic insight provided by these studies will help to define immunologic targets and therapeutic approaches applicable to future human clinical trials. PUBLIC HEALTH RELEVANCE: This project employs functional manipulation of antigen-pulsed dendritic cells to define the role of Jo-1-specific T cells in a murine model of inflammatory myopathy. This approach will clarify mechanisms of disease initiation/perpetuation and establish the feasibility of antigen- specific, dendritic cell-mediated tolerance induction. The latter objective is relevant to the treatment of multiple autoimmune diseases for which global immunosuppression is the only therapeutic option.